Power amplifier (PA) is one of the most important modules for a communication system, and along with the development of the radio communication technology, the performance of the power amplifier is more demanding than ever before.
Currently, the introduction of a high efficiency PA (HEPA) into a user equipment (UE) is being discussed by the 3rd Generation Partnership Project (3GPP) Radio Access Network 4 (RAN4), so as to reduce the power consumption and improve the heat dissipation, thereby to improve the user experience. Especially, this scheme appeals to smart phones, and FIG. 1 shows the efficiency improvement made by the HEPA.
One primary problem for the HEPA lies in its bad linearity, with a direct form of worse out-of-band radiation than a low efficiency PA. Especially, larger adjacent channel interference (ACI) may occur in a multi-cluster transmission mode and at low power, as shown in FIGS. 2 and 3.
In the related art, an adjacent channel protection index belongs to a management requirement and the requirement on an out-of-band interference index shall not be relaxed even when an advance technique is adopted by an interferer. Hence, the only feasible method is to adopt a larger in-band power back-off so as to meet the same requirement on the out-of-band interference index, i.e., to reduce actual transmission power of the UE. However, this will bring challenges to uplink network coverage for operators and increase the cost for networking. In addition, when the HEPA is used in a frequency division duplex (FDD) mode, the out-of-band linearity of the UE will be deteriorated. When the had duplex isolation exists between an uplink and a downlink of the UE, the sensitivity of a receiver of the UE may be weakened, and downlink network coverage may be adversely affected. Hence, when the HEPA is introduced, it is required to set an additional radio frequency (RF) index (there already exists a RF index corresponding to the low efficiency PA), and at this time, there will be two RF indices for the HEPA and the low efficiency PA. However, in current UE capabilities signaling, RF capabilities information merely include information about a supported Band List, without any relevant information about a type of the PA or a PA capability level, so it is impossible for the operator to determine the type or capability level of the PA integrated into the UE. At this time, probably the actual efficiency of the PA will not be improved, and meanwhile the RF index will be relaxed and the network coverage cost for the operator will increase.
In addition, in a resource-partial-allocation mode, a difference between the power back-off values for the HEPA and the low efficiency PA may be about 10 dB. When a network-side device does not know the type and capability level of the PA and determines a corresponding power back-off value, a scheduling error may probably occur.